1. Field of the Invention
This invention relates generally to the field of analog integrated circuit design and, more particularly, to voltage reference design.
2. Description of the Related Art
Many different devices and technologies require temperature-stable reference voltages. A common circuit used to provide such a reference voltage is a bandgap voltage reference circuit. Bandgap voltage reference circuits typically operate by summing a base-emitter voltage (Vbe) of a bipolar junction transistor BJT), which has a negative temperature drift, with a thermal voltage Vt that has a positive temperature drift. The thermal voltage Vt is typically dependent on the difference between Vbe of two BJTs operating at different emitter current densities. The value of the resulting bandgap voltage Vbg (Vref) is the sum of Vbe of one BJT and a quantity proportional to the difference in Vbe between two BJTs.
Typically, the output of a bandgap voltage reference circuit has a non-zero temperature coefficient (TC) for values of temperature other than a nominal operating temperature. In some applications, errors in the output voltage that arise due to this non-zero temperature coefficient may be unacceptable. Furthermore, correction circuitry may be expensive or overly complicated. The performance of the correction circuitry itself may also be subject to errors that arise due to process variations. Accordingly, new correction techniques for bandgap voltage reference circuits are desired.